Method and mechanism for determining the moisture content of paper or other material



1,708,073 MOISTURE A. A ANISM FOR OF PAPER LLEN DETERMINING T METHOD AND MECH HE CONTENT OR OTHER MATERIAL I April 9, 1929.

Filed May 1925 12w; 219? Mela Patented Apr. 9, 1929. 71

UNITED STATES PATENT OFFICE.

ALBERT ALLEN, OF BANGOR, MAINE, ASSIGNOR, BY MESNE ASSIGNMENTS, TO AT- LANTIC PRECISION INSTRUMENT COMPANY, OF BOSTON, MASSACHUSETTS, A COR- PORATION OF MASSACHUSETTS.

METHOD AND MECHANISM FOR DETERMINING THE MOISTURE CONTENT OF PAPER OR OTHER MATERIAL.

Application filed. May 1,

This invention has for its object to provide a method and means for continuously ascertaining and indicating the moisture content of travelling or moving material.

In the production of paper, for example, it

is highly desirable to secure a running indication of the moisture content thereof, without the necessity of removing sample tear cuts for test purposes, so that by appropriate controlling means the moisture content may be kept within fairly minute limits of tolerance. Likewise it is desirable to secure a similar indication of the moisture content of many other materials which may be progressively moved or fed relatively to the indicating mechanism. By employment of the method and means, which are hereinafter described, it is possible to obtain a continuous indication of the moisture content of moving material Without affecting the material in any Way and without interruption of its progress. In general, it may be stated that the result is accomplished by relating successive portions of the material to an element quickly responsive to variations in the moisture content thereof, and measuring or indicating the condition of this element or changes therein due to moisture changes in the successive portions of said material. In carrying out my process I preferably, though not necessarily, utilize in measuring and indicating variations in the moisture responsive element, electrical means which are highly responsive to such variations. I will first briefly explainthe principles of operation of a mechanism having electrical indicating means and then describe in detail the utilization of the invention in measuring and indicating the 0 moisture content of a travelling Web of paper, which has been selected as one of the materials Whose moisture content it is desirable to measure or ascertain.

If a dielectric be positioned between two spaced electrically conductive plates, a condenser is formed having electrical characteristics dependent on the area of the opposed surfaces of the plates, their spacing and the nature of the dielectric. Hence, if

an element capable of absorbing and giving olf moisture readily be used for the dielec- 1925. Serial No. 27,326.

trio, the electrical characteristics of the condenser will'vary, depending on the amount of moisture in this element since this moisture variation changes the nature of the dielectric.

Accordingly in the apparatus Which I have shown as exemplifying one embodiment of the present invention, therefore, I

preferably employ a condenser having a dielectric quickly responsive to moisture conditions and subject the dielectric to the moisture conditions of the web so that its own moisture content will bear at least some substantial relation thereto. lVhile a condenser possesses various electrical characteristics variable With the nature of the dielectric, one of these characteristics which is perhaps more easily utilizable than others for the purpose of this invention is capacity. In the embodiment of the invention hereinafter more fully described, the capacity effects due to moisture in a hygroscopic or hygrometric dielectric have therefore been utilized, though it should be recognized that the utilization of any other electrical characteristic or characteristics which varies With changes in the moisture content of a material are within the broader aspects, scope and spirit of the present invention.

lVhile various methods of measuring capacity and indicating changes therein due to changes in the dielectric might be suitable, one which particularly sensitive and well suited for the present purposes comprises utilizing the condenser as a tuning element for a high frequency oscillatory electric circuit, changes in the capacity of the condenser acting to vary the frequency and conversely, the Wave length of the circuit. These changes of frequency are capable of ready indication, so that the mechanism may be caused to act as a sensitive hygrometcr.

Figure '1 represents a fragmentary perspective View showing a portion of the mechanism of this invention.

Figure 2 is a detail section to an enlarged scale on line 22 of Figure l, but illustrating also wiring diagrams of the dielectrical circuits associated therewith.

Figure 3 is a detail section to an enlarged scale on line 33 of Figure 1.

Figure 4 is a detail in perspective showing the construction of the hygroscopic dielectric element.

At 1 is indicated a pair of spaced bars or pipes over which the web of paper as at A passes. These bars or pipes may be supported in suitable brackets 2 ad acent to their ends. Preferably slidable along these bars 1 is an open top receptacle 3 having its opposite edges 4 formed to bear on the bars 1. Seated within this receptacle and positiened entirely below its upper edge is a condenser comprising a lower imperforate metal plate 5 and an upper perforated plate 6. These plates may be fixed to the base portion 7 of the receptacle as by means of bolts 8 of insulating material, such as bakelite, passed through their corner portions, washers 9 of insulating material being positioned between these plates in order to hold them the desired distance apart. At opposlte sides of the plates 5 and 6 and fixed to the base 7 are shown anchorage strips 10 to which are fixed the ends of hygrometric dielectric material 11. The walls of the receptacle constitute a shield to protect the hygrometric element from other moisturedetermining influences than those of the material whose moisture content is being determined.

Any suitable hygroscopic dielectric may be employed, but particularly suitable for this purpose have been found strands made from reverted cellulose such as is commonly known as artificial silk. A construction which has been found applicable for the purpose is an artificial silk ribbon, the ends of which have been dipped in material such as sealing wax shown at 12 in Figure 4. The edges of the ribbon are then out between these ends and the filler strands removed leaving only the warp strands extending across between the end portions 12. These end portions may then be fixed to the anchorage strips 10 by any suitable means, such as screws 13. If desired, this dielectric may be treated with hygroscopic salts, such as cobalt chloride, to increase its sensitiveness to moisture changes. 2

This construction thus forms a condenser having between its spaced conducting plates 5 and 6 a permanently located dielectric material capable of absorbing and giving off moisture in accordance with the surrounding atmosphere. In the construction described and shown this atmosphere is that within the receptacle 3 and its humidity is controlled by the moisture content of the web passing over the open top of the receptacle, the receptacle acting to confine an atmosphere into contact with whichsuccessive portions of the web are brought as the web travels and by the motion of which the atmosphere is rapidly circulated about the hygrometric dielectric body of the condenser.

Any variation in the electrical characteristics of this condenser is therefore dependent on variations in the moisture content of the dielectric material, which is in some measure proportional to moisture variations in the web. Since all the other conditions are constant, a measurement of any of these variable characteristics is therefore, a measure of the moisture content alone of the web, and changes in moisture content of the web are represented by corresponding changes in such electrical characteristics. The characteristic which is probably the easiest to use for the purpose of obtaining an indication is that of capacity and in order to obtain such an indication of suflicient sensitivencss to show small changes in moisture content, the capacity may be used as the tuning element of an oscillatory electric circuit acting to control the frequency of the oscillations of the circuit. In order to utilize the condenser in this manner it may be used in connection with a sending or exciting and a receiving or pick up circuit such as may be employed for radio work.

Referring to Figure 2 a sending circuit of this nature is illustrated at S and may be of any suitable type for producing electrical oscillations of the desired frequency. As shown this sending circuit comprises a three element tube at having a filament or A battery 26 and a plate or B battery 27 and tuning devices comprising an inductance 28 and a capacity 29. As shown this capacity is variable for the purpose of varying the frequency of the circuit as may be desired. The grid 30 is connected through a grid leak 81 with a coil 32 in inductive relation to the coil 28 and is connected to the filament circuit. A resistance 33 is placed in series with the B battery 27 for the purpose of protccting the tube and about this may be shunted a by-pass condenser 34 to permit the passage of high frequency currents. This transmitting set which, as shown, is of regrncrative type may be shielded as by the shield 35 and projecting outside of this shield is shown a loop 36 which forms in effect a continuation of the coil 28 and serves as the coupling connection for the closed receiving circuit shown at It. This receiving or pickup circuit comprises a coil 40 coupled loosely to the loop 36 and tuned by means of the rariable condensers A and +12, one of these being a Vernier condenser, and also by the condenser formed by the plates 5 and (5 and the hygroscopic dielectric 11. Coupled to this pick-up circuit through the transformer 43 is a current indicating means such as a then mo-galvanometer 45.

Assuming now that the sending circuit is transmitting oscillations at any desired frequency, the condensers 41 and 42 may be ad usted until the circuit R is in resonance with the circuit S, whereupon the current Cal flow through the instrument 45 is a maximum. If now the dielectric 11 be subjected to a change of moisture content conditions as from the moisture of the web of paper passing thereover, it absorbs or gives up moisture, and the capacity of this condenser changes, thus throwing the circuit R out of resonance with the circuit S and decreasing the value of the current through the instrument 45. The condensers 41 and 42 may then be adjusted to bring the circuit R again into resonance with the circuit S, whereupon the change of setting of the condensers 41 and 42 will represent a capacity change due to the change of moisture in the hygroscopic dielectric responsive to the changes in moisture content of the web. As both an increase and a decrease of capacity of the tuning condenser when the circuits are in resonance would throw the circuits out of resonance and thus decrease the reading of the instrument 45, such decrease of itself would fail to indicate whether the moisture content of the web were increasing or decreasing. This instrument 45 may be made to indicate which is taking place, however, by so tuning the circuits that they remain on one or the other side of the resonance point, so that current variations in the instrument representmoisture variations in a corresponding direction,the particular direction depending on which side of the resonance pointthe circuits are maintained. If this is done, and other conditions are maintained constant, the instrument 45 may be calibrated directly in moisture content of the web.

\Vhile I have described the process and apparatus as they are employed for ascertaining and indicating the moisture content of a moving sheet of paper, I do not, of course, limit myself to their employment for the determination of the moisture content of paper only; for itwill readily be perceived tha they may be employed for a like purpose in connection with any material which can be progressively fed or moved into such relation to the hygrometric material as to.

effect a proportional change in the moisture content therein. As herein illustrated and described, the variations in the moisture content of a hygromet-ric element responsive to variations in the moisture content of successive portions of the moving material brought into. relation thereto, cause or induce consonant changes of capacity in a tuned oscillatory circuit, so that by exciting in the tuned circuit electrical oscillations which in amplitude are sensitively responsive to changes in said capacity and measuring the amplitude of such responses by an appropriate instrument in terms of moisture content, the moisture content of the moving material is indicated.

Having thus described an embodiment of this invention it should be evident to those skilled in the art that various changes and modifications may be inade therein without departing from its spirit or scope as defined by the appended claims.

I claim:

1. A hygrometer comprising a condenser having a dielectric of hygroscopic material.

2. A condenser having a dielectric of reverted cellulose.

3.. A condenser having a dielectric of reverted cellulose which is exposed to atmospheric conditions outside of said condenser.

4. A condenser comprising spaced conductive elements, and an intermediate dielectric of hygrometric material exposed on its surface to atmospheric conditions outside of said conductive elements.

/ 5. A hygrometer comprising a condenser having a dielectric of reverted cellulose treated with a hygroscopic salt.

6. A condenser comprising a pair of spaced plates, and a dielectric of hygroscopic material therebetween, one of said plates being perforated to'permit ready access of air to said dielectric.

7. An apparatus of the class described comprising an oscillatory electric circuit, variable means for tuning said circuit the value of the variation of which means is responsive to variations of moisture conditions only, and means for indicating the frequency of said circuit in terms of such moisture conditions.

8. apparatus of the class described comprising an oscillatory electric circuit, variable means for tuning said circuit the value of the variations of which means is responsive to variations of moisture conditions only, and means for indicating variations in frequency of said circuit from a standard frequency in terms of such moisture content. I

9. A mechanism of the class described comprising an oscillatory electric circuit, means for tuning said circuit comprising a condenser variable in capacity in response to variations in moisture conditions only, and means for indicating the variations in frequency of such circuit.

10. A mechanism of the class described comprising a chamber open at one side, means for passing a web of moist sheet material across said open side, a condenser in said chamber having a dielectric of hygroscopic material exposed to moisture of the web, and means for indicating electrical characteristics of said condenser and changes therein due to moisture conditions of said dielectric.

11. A mechanism of the class described comprising a pair of guide bars, an open sided container adjustable along said bars, means for passing a web of sheet material across'said bars over the open side of said container, a hygroscopic element permanently located within said container and subject to moisture conditions in said sheet, and means for indicating the moisture content of said element.

12. A mechanism of the class described comprising a chamber open on one side, means for passing a web of sheet material over said open side, a condenser in said chamber having a hygroscopic dielectric, an oscillatory electric circuit, a receiving 'circuit coupled to said oscillatory circuit and tuned by said condenser, and means for indicating current flow in said receiving circuit and changes therein produced by frequency changes in said receiving circuit relative to that in said oscillatory circuit.

13. A mechanism of the class described comprising a chamber, means for feeding material in such relation to said chamber as to subject the interior thereof to moisture conditions proportional to those of said material whose moisture content is to be tested, a device including a hygrometrie element permanently located within and exposed to moisture conditions within said chamber, said device having electrical characteristics dependent in amount on the moisture content of said element, and means for indicating the amount of such characteristics.

14. A mechanism of the class described comprising a chamber, means for subjecting the interior of said chamber to moisture conditions produced by material the moisture content of which is to be tested, a device including a hygrometric element permanently located within said chamber, said device having electrical characteristics dependent in amount on the moisture content of said element, and means for indicating in terms of the moisture content of the material the amount of such characteristics.

15. An apparatus of the class described, comprising an oscillatory electric circuit, means for progressively relating successive portions of material to said circuit, means for causing the moisture content only of successive portions of said web as they are successively related to said circuit to aifect the frequency of the oscillations therein, and means for continuously measuring and indicating such effects.

16. A mechanism for determining and indicating the moisture content of a material, which comprises a condenser having as its dielectric a hygrometric substance arranged in such relation to the travelling material as to be responsive to variations in the moisture content thereof, and means for indicating the capacity of such condenser.

17. A mechanism of the class described, comprising a chamber, means for subjecting the interior of said chamber to moisture conditions proportional to those of a material the moisture content of which is to be determined, and a hygrometric substance exposed to the moisture conditions of the interior of said chamber, said mechanism including a condenser depending in capacity on the moisture content of said substance, and means for measuring said capacity.

18. Mechanism for determining and indicating the moisture content of a running body of material, which comprises a hygrometric substance with which said body is progressively placed in responsive relation, said mechanism including a condenser variable in capacity in accordance with the moisture content of said substance, and means for indicating the variable capacity of said condenser.

19. Mechanism for determining and in dicating the moisture content of material, which comprises a permanently located hygrometric substance, means for progressively moving said material to bring successive portions thereof into relation thereto to cause said hygrometric substance to have a moisture content proportional to that of said material, and means for continuously indicating the moisture content of said hygrometrical material.

20. Mechanism for determining and indicating the moisture content of moving material, which comprises a permanently located hygrometric substance with which successive portions of said material is related, means for moving said material, said mechanism including a device having electrical characteristics dependent in amount on the moisture content of said hygrometric substance, and means for continuously indicating the amount of such char acteristics.

21. Mechanism for determining and indicating the moisture content of material, comprising a condenser having a hygrometric substance between the plates thereof, means for moving successive portions of said material into relation to said hygrometric substance to cause said hygrometric substance to contain moisture proportional to that of the said portions, and indicating means responsive to variations in capacity of said condenser.

22. Mechanism for determining and indicating the moisture content of material, comprising spaced conductive plates and a hygrometric dielectric substance arranged between them, thereby forming a condenser variable in capacity proportional to the water content of said substances, supports between which said substance is stretched, supports for holding said condenser plates in fixed relation to each other, and means for moving successive portions of said material into relation to said hygrometrie substance to cause the latter to have a moisture content proportional to the said successive portions of said material.

23. Mechanism for determining and indicating the moisture content of material which comprises a hygrometric substance responsive to variations in moisture content of said material, means for placing successive portions of said material in proximity to said hygrometric material to cause the moisture content of the latter to correspond proportionally to that of the successive portions of said'material, said mechanism including a condenser whose capacity varies automatically in response to variations in moisture content of saidhygrometric substance, and indicating means responsive to said variations in capacity of said condenser.

24. In a mechanism of the class described, a permanently located hygrometric element, and means for progressively relating thereto a moving material whereby variations in the moisture in the successive portions of the said material produce corresponding variations in the moisture content of said hygrometric element.

25. In a mechanism of the class described, a quickly responsive permanently located hygrometric element, means for progressively moving material in such relation thereto that changes in the moisture contents of the successive portions of said material progressively presented to the hygrometric element induce responsive moisture changes in said element, a member shielding the said hygrometric element from other moisture-determining influences, and means for recognizing the hygrometric responses of said hygrometric element.

26. In a mechanism of the class described, a quickly responsive permanently located hygrometric element, means for progressively moving material in such relation thereto that changes in the moisture contents of the successive portions of said material progressively presented to the hygrometric element induce responsive moisture changes in said element, a member shielding the said hygrometric element from other moisture-determining influences, and electrical means recognizing the hygrometric responses of said hygrometric element.

27. In a mechanism of the class described, a quickly responsive permanently located hygrometric clement, means for progressively moving material in such relation thereto that changes in the moisture con-v tents of the successive portions of said material progressively presented to the hygrometric element induce responsive moisture changes in said element, said mechanism including a condenser responsive in capacity to changes in moisture content of said hygrometric element, and means recognizing changes in said capacity.

28. In a mechanism of the class described, a quickly responsive permanently located hygrometric element, means for progressively moving material in such relation thereto that changes in the moisture contents'of the successive portions of Said material progressively presented to the hygrometric element induce responsive moisture changes in said element,"a member shielding the said hygrometric element from other moisture-determining influences, said mechanism including a condenser responsive in capacity to changes in moisture content of sald hygrometric element and means recognizing changes in said capacity.

29. In a mechanism of the class described, a quickly responsive permanently located hygrometrlc element, means for progressively movlng material in such relation thereto that changes in the moisture contents of the successive portions of said material progres- SIVBly presented to the hygrometric element induce responsive moisture changes in said element and means for recognizing the hygrometric responses of said hygrometric element, comprising in combination :-a tuned oscillatory electric circuit whereof the capacity is variable, consonant with the moisture variations of the hygrometric element, means for exciting electrical oscillations in said tuned circuit which in amplitude are sensitively responsive to variations in said.

capacity and means for indicating the amplitude of the said oscillations.

30. A mechanism of the class described comprising a variable condenser formed of a pair of spaced conductive plates, and a' hygrometric dielectric between said plates, the moisture content of which dielectric is responsive to the moisture content of material to be tested; a closed inductance-containing circuit in which said condenser is a tuning element, a regenerative oscillatory exciting circuit near resonance with said closed circuit and coupled thereto, and means for measuring the current induced in said closed circuit by said exciting circuit as a measure of the moisture content of said material.

31. A mechanism of the class described comprising a variable condenser formed of a pair of spaced conductive plates, and a hygrometric dielectric between said plates, the moisture content of which dielectric is responsive to the moisture content of material to be tested; a closed inductance-containin'g circuit in which said condenser is a tuning element, a regenerative oscillatory exciting circuit near resonance with said closed circuit and coupled thereto, and a thermometer for measuring the current induced in said closed circuit by said exciting circuit.

32. A mechanism of the class described, comprising means for continuously moving material, the moisture content of Which is to be determined, a variable electrical condenser comprising a pair of spaced conductive plates and a hygrometric dielectric besponsive in moisture content of successive portions of said material as they are moved therepast, a closed inductance-containing circuit in'which said variable condenser is a tuning element, an oscillatory regenerative exciting circuit near to resonance with said closed circuit and coupled thereto, and means for indicating the current flow in said closed circuit induced by said exciting circuit.

A hygrometer having a moisture responsive element composed of reverted cellulose.

34. A hygrometer having a moisture responsive element composed of reverted cellulose treated with a hygroscopic salt.

A hygrometer having a moisture responsive element composed of filaments of reverted cellulose.

36. A hygrometer having a moisture responsive element composed of a ribbon of filaments of reverted cellulose, the filler strands intermediate its ends having been removed.

37. A hygrometer having a moisture responsive element composed of a ribbon of filaments of reverted cellulose, the filler strands intermediate its ends having been removed, and means for engaging the ends of said ribbon for holding it in position.

38. A hygrometric device consisting of a condenser comprising a pair of spaced plates, and a dielectric between said plates composed of reverted cellulose.

39. A hygrometric device consisting of a condenser comprising a pair of spaced plates, and a dielectric between said plates composed of a series of filaments of reverted cellulose extending lengthwise between said plates.

40. The method of determining the mois ture content of a length of material, which comprises subjecting to the influence of said length of said material a permanently located hygrometric element capable of rapidly absorbing or giving off moisture so as to contain an amount proportional to that of said sheet material, and measuring the moisture content of said body.

41. The method of determining the moisture content of a sheet of material, which comprises progressively subjecting to the influence of lengthwise portions of said material a permanently located hygrometric element capable of absorbing and giving off moisture so as to contain moisture proportional to that of the portions of material to the influence of which it is subjected, and indicating the moisture content of said element.

42. The method of continuously deter mining and indicating the moisture content of travelling material of indeterminate length, which comprises progressively relating such material to an element respon sive to moisture conditions of the related portion and having electrical characteristics dependent on such response, and continuousl measurin and indicatin such chary a c acteristics.

43. The method of determining the moisture content of a length of material, which comprises relating to such material a body rapidly responsive to moisture conditions in such material and having electrical characteristics dependent on such response, and measuring such characteristics.

44. The method of continuously determining and indicating the moisture content of traveling material, which comprises progressively relating portions of such material to an element responsive to moisture conditions only of the related portions, and continuously measuring and indicating the extent of such response.

45. The method of measuring the moisture content of a length of material, which comprises causing the moisture content only of such material to affect a characteristic of an electric current, and measuring such characteristic effects.

46. The method of continuously measuring and indicating the moisture content of moving material of indeterminate length, which comprises causing the moisture content only of successive portions of the material to affect a characteristic of an electric current, and continuously measuring and indicating such characteristic effect.

47 The method of measuring the moisture content of material, which comprises causing such moisture content only to affect the frequency of an alternating electric current and measuring the frequency change due to such effect.

48. The method of continuously measuring and indicating the moisture content of material of indeterminate length, which comprises causing the moisture content of successive lengths of such material to affect the frequency of an alternating electric current, and continuously measuring and indicating such frequency eflects.

49. The method of measuring the moisture content of material, which comprises contacting with such material a confined atmosphere also contacting with a hygrometric body, and measuring the moisture content of said body.

50. The method of continuously measuring the moisture content of traveling material, which comprises contaeting with successive portions of such material a confined atmosphere also contacting with a hygrometric body, and continuously measuring the moisture content of said body.

51. In combination, a hygrometric element, means for progressively moving material in such relation thereto that changes in the moisture content of the successive portions of said material progressively .pre-

sented to the hygromctric element induce responsive moisture changes in said element, a member shielding the said hygrometric element from other moisture determining influence, and means for recognizing the total moisture and variations of total moisture of said hygrometric element.

52. In ombination, a solid hygrometric clement, means for progressively moving material in such relation thereto that changes in the moisture content of the successive portions of said material progressively presented to the hygrometric element induce responsive moisture cl'la-nges in said element, a member shielding the said hygrometric element from other moisture determining influence, and means for directly recognizing the total moisture and variations of total moisture of said hygrometrie element.

53. A device for measuring the moisture content of a traveling Web which comprises means including said Web for enclosing a body of air in intimate contact with the surface of said web, a hygrometric element held in said body of air and about which said air is circulated by the movement of said web, and indicating means responsive to the moisture content of said element.

54:. A mechanism for determining and indicating the moisture content of moving material, comprising a hygrometric dielectric substance, supports on which such substance is placed, condenser plates between which said hygrometric substance is located, means for moving successive port-ions of said material into proximity to said substance to cause the latter to have a moisture content proportional to that of said portions of said material, and means for indicating variations in capacity of the condenser formed by said plates and said substance.

In testimony whereof I have aflixed my signature.

ALBERT ALLEN. 

